Fix superDevMode in IE8

Bug: issue 8907
Change-Id: I158a90995634bb02023d6ce6c7bcbd478ee1930f

dev/codeserver/java/com/google/gwt/dev/codeserver/dev_mode_on.js

diff --git a/dev/codeserver/java/com/google/gwt/dev/codeserver/dev_mode_on.js b/dev/codeserver/java/com/google/gwt/dev/codeserver/dev_mode_on.js
index cf434a3..8f31071 100644
--- a/dev/codeserver/java/com/google/gwt/dev/codeserver/dev_mode_on.js
+++ b/dev/codeserver/java/com/google/gwt/dev/codeserver/dev_mode_on.js
@@ -478,7 +478,8 @@
     function onPollFinished(event) {
         if (compiling && event.status == "compiling") {
             dialog.updateProgress(event);
-            var waitTime = 1000 - (Date.now() - lastPollStart);
+            // Date.now() fails in IE8
+            var waitTime = 1000 - (new Date().getTime() - lastPollStart);
             if (waitTime > 0) {
                 setTimeout(poll, waitTime);
             } else {
@@ -490,7 +491,8 @@
 
     function poll() {
       if (compiling) {
-          lastPollStart = Date.now();
+          // Date.now() fails in IE8
+          lastPollStart = new Date().getTime();
           callJsonp(codeserver_url + 'progress?', onPollFinished);
       }
     }

dev/codeserver/java/com/google/gwt/dev/codeserver/stub.nocache.js

diff --git a/dev/codeserver/java/com/google/gwt/dev/codeserver/stub.nocache.js b/dev/codeserver/java/com/google/gwt/dev/codeserver/stub.nocache.js
index 9a9020c..516308b 100755
--- a/dev/codeserver/java/com/google/gwt/dev/codeserver/stub.nocache.js
+++ b/dev/codeserver/java/com/google/gwt/dev/codeserver/stub.nocache.js
@@ -203,7 +203,8 @@
     // in IE, and to avoid the same function being called twice.
     var callbackName = '__gwt_compile_callback_' + moduleIdx + '_' + new Date().getTime();
     $wnd[callbackName] = function(r) {
-      delete $wnd[callbackName];
+      // IE8 fails if we use delete
+      $wnd[callbackName] = undefined;
       // Avoid running callback if response came after timeout
       if (!expired) {
         clearTimeout(timeoutId);